1. Field of the Invention
The present invention relates to a display apparatus, and more particularly to a touch panel display apparatus and a fabricating method thereof.
2. Description of the Related Art
In typical applications for touch panel display apparatus, voltage or current signals are generated corresponding to a position that is pressed on the panel with a stylus pen or a finger, the signals thereby inputting an order or graphic information designated by a user. A resistive touch panel with an analog input method is commonly used, and is integrated with a liquid crystal display panel, such as a flat panel display. The liquid crystal display panel generally controls a light transmittance of liquid crystal cells interposed between two glass substrates to display an image. Each of the liquid crystal cells response to a video signal, i.e., a corresponding pixel signal to control the volume of transmitted light.
FIG. 1 a perspective view of a touch panel apparatus mounted on a liquid crystal display panel according to the related art. In FIG. 1, a touch panel 32 is mounted on a liquid crystal panel 31 and a backlight 33. The touch panel 32 is electrically connected to a computer system 35 via a touch controller 34 and signal lines 36. Accordingly, during operation of the touch panel 32, a voltage value of a contacted position is calculated at the touch controller 34 to recognize coordinates of the contacted position.
FIG. 2 is a cross sectional view of the touch panel apparatus of FIG. 1 according to the related art. In FIG. 2, the liquid crystal display panel 31 includes an upper plate 31a and a lower plate 31b, and the touch panel 32 includes an upper plate 32a and a lower plate 32b, and a polarizer 4 is formed between the liquid crystal display panel 31 and the touch panel 32.
The liquid crystal panel 31 includes liquid crystal material 14 and spacers 5 interposed between the lower plate 31b and the upper plate 31a. A gate line 6, an insulation film 8, a pixel electrode 10a, and a first alignment film 12a are sequentially formed on a lower substrate of the lower plate 31b. The upper plate 31a includes a black matrix 16, a color filter 18, a common electrode 10b, and a second alignment film 12b sequentially formed on the bottom surface thereof. The spacer 5 is formed on the first alignment film 12a before the upper plate 31a is bonded with the lower plate 31b. The spacer 5 separates the upper plate 31a from the lower plate 31b by a uniform gap, thereby creating a uniform thickness of the liquid crystal material 14.
The touch panel 32 includes a spacer 28 formed between the lower plate 32b and the upper plate 32a, and may include a polyethylene terephthalate (PET) film. On a lower sheet 20 of the lower plate 32b is formed a lower transparent film 26, and on an upper sheet 24 of the upper plate 32a is formed an upper transparent film 27. The upper sheet 24 is formed of PET and the lower sheet 20 is formed of one among glass, plastic and PET. The upper and lower transparent films 27 and 26 are formed of transparent conductive material with good transmittance. For example, one of indium-tin-oxide ITO, indium-zinc-oxide IZO and indium-tin-zinc-oxide ITZO.
An upper electrode layer is formed at the end of the upper transparent film 27, and a lower electrode layer is formed at the end of the lower transparent film 26. The upper electrode layer is short-circuited from the lower electrode layer when the upper sheet 24 is pressed by a stylus pen or a finger, thereby generating a current or voltage level signal that varies in accordance with the pressed position. In addition, the upper and the lower electrode layer is formed of a metal material with good conductivity, such as silver Ag. The upper and the lower transparent films 27 and 26 are both formed with an amorphous ITO structure or a crystalline ITO structure.
The polarizer 4 is formed between the lower plate 32b of the touch panel 32 and the upper plate 31a of the liquid crystal display panel 31, and converts visible light into linear polarized light at the both sides of the liquid crystal display panel 31. A first adhesive 1a is formed between the polarizer 4 and the lower plate 32b of the touch panel 32, and a second adhesive 1b is formed between the polarizer 4 and the upper plate 31a. 
FIG. 3 is a plane view of an electrode and signal line formed on the touch panel of FIG. 2 according to the related art, and FIG. 4 is a perspective view of upper and lower plates of the touch panel of FIG. 3 according to the related art.
In FIGS. 3 and 4, the upper plate 32a (in FIG. 4) of the touch panel 32 includes X-axis electrodes 27a and 27b formed at the edge thereof along a vertical direction, and signal lines 28c and 28d derived from the center of the X-axis electrode 27a and 27b for supplying the signal with the current or the voltage level to the touch controller 34. The lower plate 32b (in FIG. 4) of the touch panel 32 includes Y-axis electrodes 26a and 26b formed at the edge thereof along a horizontal direction, and signal lines 28a and 28b derived from the center of the Y-axis electrodes 26a and 26b for supplying the signal with the current or the voltage level to the touch controller 34. The signal lines 28a, 28b, 28c, and 28d include a tail part and an electrode extension connected to the electrodes 26a, 26b, 27a, and 27b. Accordingly, the signal lines 28a, 28b, 28c, and 28d derived from the center of the electrodes 26a, 26b, 27a, and 27b extend to one side of the touch panel 32 for make connection to a touch panel controller (not shown).
When the upper and the lower transparent films 27 and 26 of the touch panel 32 are formed of amorphous ITO, the upper and the lower transparent film 27 and 26 have low durability and low wear-resistance. Accordingly, if the touch panel apparatus 32 is used for a long period of time, the upper and lower sheets 24 and 20 begin to separate from the upper and the lower films 27 and 26. Thus, the linearity of the voltage detected from the upper and the lower electrode layers is disrupted. On the other hand, when the upper and the lower transparent films 27 and 26 are formed with the crystalline ITO structure, the transparent films have a flexible property. Such crystalline structure can be formed by depositing ITO material and treating with heat at a high temperature below the melting point. The ITO material has an amorphous structure when depositing the ITO material, and the heat treatment changes it to a crystalline structure. In addition, since the upper and the lower transparent films 27 and 26 of the crystalline ITO structure are flexible, they are not durable. Accordingly, the ITO film easily deteriorates when the touch panel is used for a long period of time, thereby disrupting the linearity of the voltage detected at the upper and the lower electrode layers.